1. Field of the Invention
The invention relates to an electrochemical storage cell of the alkali metal and chalcogen type with at least one anode chamber and one cathode chamber. Each chamber is provided with at least one current collector. The chambers are separated from each other by an alkali-ion-conducting solid electrolyte and bounded at least in some areas by a metallic housing.
2. Description of the Prior Art
Such rechargeable electrochemical storage cells with solid electrolytes are highly suitable for the design of high-energy storage cells with high power density. Such storage batteries are being used increasingly as the electric energy source for electric vehicles. The solid electrolytes used in the alkali/chalcogen storage cells, which are made, for instance, of beta-aluminum oxide, are characterized by the feature that the partial conductivity of the mobile ion is very high and the partial conductivity of the electrons is smaller by many powers of ten. The effect of the use of such solid electrolytes for the design of electrochemical storage cells is that practically no self-discharge takes place, since the electron conductivity is negligibly small and the reaction substances as neutral particles also cannot get through the solid electrolyte.
For the manufacture of storage cells and high-temperature storage batteries, a multiplicity of such electrochemical storage cells are wired together. In high-temperature storage cells for electric vehicles, for instance, it is necessary to connect many electrochemical storage cells in series and only few storage cells in parallel. Reasons therefor are that the energy content of such a high-temperature storage battery will generally be smaller than 40 kWh, but the energy content of a single storage cell will be larger than 80 Wh. It follows that such a high-temperature storage battery will contain not more than 500 storage cells. If the individual storage cell has a voltage of about 2 V and a total of 200 V is to be generated with such a battery, then 100 storage cells must be connected in series. This means that at most 5 storage cells can be connected in parallel. If an overload occurs in one or more storage cells of this series circuit, the temperature in the interior of the storage cell is increased. A temperature rise above the operating temperature of the storage cell can, however, lead to its destruction. The resistance of such a defective cell becomes high, whereby the overall current flow through the series circuit in which this storage cell is located, is interrupted.
German Published Non-Prosecuted Application DE-OS No. 28 19 583 discloses an electrochemical storage cell having a circuit which is interrupted if the temperature of the storage cell rises substantially above its operating temperature. In this storage cell, at least one of the two current collectors consists of two parts. The first part is arranged outside, and the second part inside the storage cell. The two parts are connected together via an electrically conducting contact element which melts at a temperature which is above the operating temperature of the storage cell by a presettable amount. Thereby, the circuit through the storage cell is interrupted. It is a disadvantage here that the electric conductivity of the current collector is reduced by the subdivision into several sections, particularly by the insertion of a fusible contact element, because corrosion at the contact points can lead to a reduction of the conductivity.